Electrical furnace



March '20, 1934. H. GEORGE ET AL ELECTRICAL FURNACE Filed Feb'. 18, 1933 Eiql.

INVENTORS ///V/?/ GEORGE ATTORNEY Patented Ma. 20, 1934' ELECTRICAL FURNACE Henri George, Paris, and Gaston'Delpech, Clamart, France, assignors to Societe Anonyme Des Manufactures Des Glaces & Produits Chimiques De Saint-Gobain, Chauny & Cirey, Paris, France Application February l8, 1933, Serial No. 657,366 In France February 19, 1932 4 Claims. (CI. 13-20) which is preferably made of a piece of graphite cut into theform of a helical coil or any other suitable shape. h

In furnaces of this type used in prior art the electrical heating element was supported at its two ends by immovable members which were connected to the poles of a source of electrical energy. When an electrical current is passed through this element it becomes heated and expands due to the influence of heat. Since there is no room provided for this expansion, considerable inner forces are developed within the heating element, which subject the windings of the helical resistance to tension and often cause the breakage of these windings.

An object of this invention is to provide means which will firmly support an electrical resistance and at the same time allow it to expand freely, thus eliminating the disadvantages of constructions used heretofore.

Another object is to provide an electrical furnace of a simple and durable construction and provided with electrical resistances which can be overheated without the danger of breakage.

A further object is to increase the durability of electrical resistances made of carbonaceous material by providing suitable supporting means for such resistances.

The above and other objects of this invention may be realized by connecting one end of a support with one end of an electrical resistance in such a. way that the expansion of both these members can take place in the direction of their interconnected ends; the central axis of this support, which has preferably the form of a tube or a prism, coincides with the central axis of the electrical resistance and the support either surrounds the resistance or is located within it, depending upon the construction of the furnace.

We prefer to use screw-threads for connecting the electrical resistance with the support, as well, as for connecting the resistance and the support with the terminals used for supplying the electrical current to the resistance, since screw threads increase the contacting areas of these parts We prefer to use amorphous carbon such as oil coke, petroleum coke, or coke made in retorts as the material out of which the terminals supplying the electrical current to the resistance are made, due to the excellent properties of this material.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showing by way of example only, preferred embodiments of the inventive idea.

In the drawing:

Figure 1 is an axial section through a furnace made in accordance with the principles of this invention.

Figure 2 shows in section another modification of the inventive idea.

In the furnace shown in Figure 1 the heat emitted by the heating element or the electrical resistance 3 is radiated towards the interior of this resistance. The resistance 3 is cut into the form of a helical coil and is connected by screw threads at one of its ends with a plug 4 which is screwed into a block 5. A tubular support or heating element 6 surrounds the resistance 3 and is concentrical with respect to said resistance. The other end of the resistance 3 is connected to the support 6 by means of screw threads, while the support 6 is screwed into a collar 7 which sur-' rounds a part of the block 5. In other words, the resistance 3, the support 6 and the collar '7 are connected in series with each other. The resistance 3, the tubular support 6 and the plug 4 are preferably made of graphite. The block 5 and the collar '7 are made of amorphous carbon and carry the metallic terminals 8 and 9, respectively.

The collar 7 is rigidly connected with a plurality of bent projections or tongues 10 which carry the movable adjusting screws 11. An insulation 12 is carried by the block 5 and is situated between the block 5 and the adjusting screws 11. The object of the screws 11 is to maintain the collar '7 and the support 6 at the same predetermined distance from the block 5 and the resistance 3. ,Pieces of insulation 13 and 14 are placed between the block 5 and the collar 7 and are used to prevent air from entering into the 'annular space formed between the resistance 3 trical energy a current flows through the block- 5, the plug 4, the electrical resistance 3, the tubular support 6 and the collar '7. A short circult between the terminals 8 and 9 is prevented through the provision of insulation 12, 13 and 14. The electrical current will heat the resistance 3 and the heat waves prevented from being radiated into the open by means of heat insulation 1'7 will heat the space surrounded by the windings of the resistance 3. The resistance 3 and the support 6 will expand simultaneously due to the influence of the heat. Since that end of the resistance 3 which is connected with the tubular support 6 remains free and is situated a certain distance from the ring 15, the resistance 3 and the support 6 will gradually expand in that direction, thus diminishing the width of the slit 21 formed between the ring 15 and the resistance 3.

, The modification shown in Figure 2 of the drawing shows parts of an electrical furnace in" which the heat waves radiated by a heating element or a resistance 22 are directed towards the exterior thereof. The resistance 22 has the shape of a helical coil and is screwed at one of its ends upon a tubular support or heating element 23; the

v place.

trated in the drawing may be overheated to a resistance 22 and the support 23 have a common central axis. The tubular support 23 is connected at its other end with a collar or ring 24, while the other end of the resistance 22 is connected by screw threads with a collar or ring 25. The collars 24 and 25 are separated from each other by insulation 26.

The resistance 22 and the tube 23 are preferably made of graphite while the collars 24 and 25 are made of amorphous carbon.

If the collars 24 and 25 are connected with a source of electrical energy, not shown in the drawing, an electrical current will flow through the collar 24, the tubular support 23, the electrical resistance 22 and the collar 25. A short circuit between the collars 24 and 25 is prevented through the provision of insulation 26. The electrical resistance 22 and the tubular support 23 can expand freely-without developing inner forces since those ends of the two members which are connected with each other are not'connected to any other part of the furnace, so that these ends can move while expansion and contraction take The electrical furnaces of the type illusconsiderable extent and for a long period of time without any damage to the heating elements and to the other parts connected with these elements.

,What is claimed is:

In an electrical furnace, a heating element made of graphite, another heating element made of graphite and concentrical with respect to the first-mentioned heating element, the second-mentioned heating element being connected at one 'of its ends with an end of the first-mentioned heating element, and means for supplying electrical current to the heating element, said means being connected with the second-mentioned heating element at the opposite end thereof, the interconnected ends of the heating elements being free from'contact with any parts of the furnace to consisting of the same material and concentrical' with respect to the first-mentioned heating element, a member adapted to be connected to one of the poles of a source of electrical energy, and another member adapted to be connected to the other pole of said source of electrical energy, the first-mentioned member, the second-mentioned heating element, the-first-mentioned heating element and the second-mentioned member being connected in series with each other in the order stated, the interconnected ends of the heating elements being free from contact with any part of the furnace to enable an expansion of the heating elements in the direction of their internected ends.

3. In an electrical furnace, a heating element consisting of a conducting material, another tubular heating element consisting of the same material and having a common central axis with,

the first-mentioned heating element, the secondmentioned heating element being connected at one of its ends with an end of the first-mentioned heating element, a block adapted to be connected to-a pole of a source of electrical en-' ergy, means connecting said block with the other end of the first-mentioned heating element, a collar adapted to be connected to the other pole of said source of electrical energy and surrounding said block, said collar being connected with the opposite end of the second-mentioned heating element, means maintaining said collar and said block at a predetermined distance from each other, an end member, and means connecting said end member with said collar, the interconnected ends of the heating elements being devoid of contact with any parts of the furnace to enable an expansion of the heating elements in the direction of their interconnected ends.

4. In an electrical furnace, a hollow heating member consisting of a conducting material, another tubular heating element consisting of the same material and located within the first-mentioned heating element, said heating elements having a common central axis, one end of the second-mentioned heating element being connected with one end of the first-mentioned heating element, a collar connected with the opposite end of the first-mentioned heating element, an-' other collar connected with the opposite end of the second-mentioned heating element, and insulation interposed between said collars, the interconnected ends of the heating elements being devoid of contact with any parts of the furnace v HENRI GEORGE. GASTON DELPECH. 

